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dkim=fail reason="signature verification failed" (1024-bit key) header.d=sf.net header.i=@sf.net header.b="M1AVKABp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8BD5F215A4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-f2fs-devel-bounces@lists.sourceforge.net Received: from [127.0.0.1] (helo=sfs-ml-1.v29.lw.sourceforge.com) by sfs-ml-1.v29.lw.sourceforge.com with esmtp (Exim 4.90_1) (envelope-from ) id 1imvba-00089p-Ej; Thu, 02 Jan 2020 08:13:18 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-1.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1imvbZ-00089V-5B for linux-f2fs-devel@lists.sourceforge.net; Thu, 02 Jan 2020 08:13:17 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:CC:To:Subject:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; 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Thu, 02 Jan 2020 08:13:17 +0000 Received: from DGGEMS401-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 902062E29299B644E8A3; Thu, 2 Jan 2020 16:13:04 +0800 (CST) Received: from [10.134.22.195] (10.134.22.195) by smtp.huawei.com (10.3.19.201) with Microsoft SMTP Server (TLS) id 14.3.439.0; Thu, 2 Jan 2020 16:13:02 +0800 To: Eric Biggers , References: <20191231181416.47875-1-ebiggers@kernel.org> From: Chao Yu Message-ID: <883839de-94e7-9c93-388b-9787e3fa76ba@huawei.com> Date: Thu, 2 Jan 2020 16:13:01 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20191231181416.47875-1-ebiggers@kernel.org> Content-Language: en-US X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected X-Headers-End: 1imvbX-006nZ0-0N Subject: Re: [f2fs-dev] [PATCH] f2fs: fix deadlock allocating bio_post_read_ctx from mempool X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-fscrypt@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 2020/1/1 2:14, Eric Biggers wrote: > From: Eric Biggers > > Without any form of coordination, any case where multiple allocations > from the same mempool are needed at a time to make forward progress can > deadlock under memory pressure. > > This is the case for struct bio_post_read_ctx, as one can be allocated > to decrypt a Merkle tree page during fsverity_verify_bio(), which itself > is running from a post-read callback for a data bio which has its own > struct bio_post_read_ctx. > > Fix this by freeing first bio_post_read_ctx before calling > fsverity_verify_bio(). This works because verity (if enabled) is always > the last post-read step. > > This deadlock can be reproduced by trying to read from an encrypted > verity file after reducing NUM_PREALLOC_POST_READ_CTXS to 1 and patching > mempool_alloc() to pretend that pool->alloc() always fails. > > Note that since NUM_PREALLOC_POST_READ_CTXS is actually 128, to actually > hit this bug in practice would require reading from lots of encrypted > verity files at the same time. But it's theoretically possible, as N > available objects doesn't guarantee forward progress when > N/2 threads > each need 2 objects at a time. > > Fixes: 95ae251fe828 ("f2fs: add fs-verity support") > Signed-off-by: Eric Biggers Reviewed-by: Chao Yu Thanks, _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel